1. Field of the Invention
The present invention relates to an ultrasonic bonding machine for bonding together overlapped portions of a plurality of workpieces.
2. Description of the Prior Art
U.S. Pat. No. 2,934,602 discloses a resonator support apparatus. As for the resonator support structure of this apparatus, when a nut is fastened, a wedge outer cylinder secures a resonator by shrinking force from a holder and the wedge function of a wedge inner cylinder and the wedge outer cylinder to achieve parallelism between the bonding work face to be contacted to a workpiece of the resonator and the face in contact with the workpiece of a mounting table. When the bonding work face in contact with the workpiece of the resonator is gradually worn away by repeating the processing operation of the ultrasonic bonding machine or when the bonding work face is damaged by fine foreign matter sandwiched between the workpiece and the bonding work face, a bonding failure or the damage of the workpiece occurs. To prevent this, when the bonding work face is damaged, the resonator may be exchanged with a new one, which is not economical. Therefore, one resonator is provided with a plurality of bonding work faces in a circumferential direction with an axis in a vibration transmission direction as the center so that when one bonding work face is damaged, another bonding work face can be used.
U.S. Pat. No. 2,712,592 discloses a mounting apparatus. In this mounting apparatus, while a mounting table is assembled by a bearing which is constructed by mating between a spherical projection portion and a spherical depression portion, and pressure air is supplied between the mating faces of the spherical projection portion and the spherical depression portion to form a lubricant air layer, the bonding work face of a bonding tool is pressed against the top face of the mounting table to have the mounting table follow the bonding work face of the bonding tool, the pressure air of the lubricant air layer is absorbed between the mating faces of the spherical projection portion and the spherical depression portion, and the mounting table which has made a follow-up movement is fixed to the base to maintain its position.
U.S. Pat. No. 2,841,334 discloses a bonding tool provided with a follow-up unit similar to the mounting apparatus of the above U.S. Pat. No. 2,712,592.
Since the resonator support apparatus disclosed by U.S. Pat. No. 2,934,602 has a structure that the resonator is fixed to the holder, to replace one bonding work face by another bonding work face, the fixing of the resonator to the holder is canceled by loosening a nut, and the resonator is turned in a circumferential direction with an axis in a vibration transmission direction as the center of rotation to achieve parallelism between the new bonding work face and the face to be contacted to the workpiece of the mounting table. Thereafter, the resonator must be fixed to the holder by fastening the nut again. When fastening force for fastening the nut again changes, the vibration balance of the resonator varies, whereby it takes a lot of labor and time to switch from one bonding work face to another bonding work face.
Since the mounting apparatus disclosed by U.S. Pat. No. 2,712,592 has a structure that pressure air is supplied between the mating faces of the spherical projection portion and the spherical depression portion or absorbed between the mating faces of the spherical projection portion and the spherical depression portion through the same passage, a valve for connecting the air supply system and air suction system to the same passage or disconnecting the systems from the passage needs to have functions for both increased pressure and reduced pressure, thereby making the structure of the valve complex. In addition, as this mounting apparatus has a structure that the mounting table which has made a follow-up movement is fixed to the base by the suction of air, when vibration such as ultrasonic vibration is transmitted from the bonding tool to the mounting table during processing, suction force between the mating faces of the spherical projection portion and the spherical depression portion lowers, and the position of the mounting table which has made a follow-up movement slightly deviates from its right position, thereby exerting a bad influence on processing.
Since what is disclosed by U.S. Pat. No. 2,841,334 has a structure that as the bonding tool is provided with a follow-up unit, a problem occurs that when the bonding tool is used as a tool for bonding a workpiece with ultrasonic vibration, imbalance of mass caused by the follow-up unit exerts a bad influence on ultrasonic vibration in the bonding tool, in addition to the problem of the mounting apparatus disclosed by the above U.S. Pat. No. 2,712,592. Therefore, this apparatus can hardly be employed.
It is an object of the present invention to facilitate the replacement of a bonding work face used in an ultrasonic bonding machine. It is another object of the present invention to optimize the maintenance of the position of a mounting table which has made a follow-up movement so that the top face of the mounting table becomes parallel to the bonding work face of the resonator.
In the ultrasonic bonding machine of the present invention, a resonator support device comprises a holder connected to a pressure unit, rotation support units and an angle indexing unit, the rotation support units turn the resonator with an axis in a vibration transmission direction as the center of rotation, and the angle indexing unit is fixed at an indexing angle in a circumferential direction with the axis in the vibration transmission direction of a plurality of bonding work faces of the resonator turned by the above rotation support units as the center, thereby making it possible to carry out the replacement of the used bonding work face easily. Since the angle indexing unit comprises an angle indexing body mounted to the holder in such a manner that it can move in a direction perpendicular to the axis in the vibration transmission direction, stoppers attached to the angle indexing body, and stopper portions to be mated with the stoppers at an indexing angle of the plurality of bonding work faces and formed in the rotation support unit, angle indexing can be carried out manually. When the angle indexing unit comprises an operation body rotatably mounted to the holder, a cam fixed to the operation body and a guide for slidably mating the angle indexing body with the holder, an angle indexing operation becomes easy. When the angle indexing unit comprises a step motor mounted to the holder and a train of gears for transmitting the revolution of the step motor to the rotation support unit, angle indexing can be carried out electrically. When the train of gears consists of a small-diameter gear connected to the step-motor and a large-diameter gear connected to the rotation support unit, electric angle indexing becomes more accurate. The mounting unit of the ultrasonic bonding machine of the present invention comprises a base, mounting table, bearing which consists of a spherical projection portion and a spherical depression portion and which mounts the mounting table to the base in such a manner that the mounting table can make a follow-up movement, air supply means for forming a lubricant air layer between the mating faces of the spherical projection portion and the spherical depression portion, and fixing means including a mechanical lock for fixing the mounting table which has made a follow-up movement to the base as a separate unit from the air supply means, or a follow-up unit in a portion for mounting the resonator to the pressure unit, or the follow-up unit comprises a bearing which consists of a spherical projection portion and a spherical depression portion and which mounts the resonator to the mounting table in such a manner that the mounting table can make a follow-up movement, air supply means for forming a lubricant air layer between the mating faces of the spherical projection portion and the spherical depression portion, and fixing means including a mechanical lock for fixing the mounting table which has made a follow-up movement to the base as a separate unit from the air supply means. Therefore, pressure air is supplied from the pressure air supply system to the mating faces of the spherical projection portion and the spherical depression portion to form a lubricant air layer, the holder is lowered along a straight line by the pressure unit, the bonding work face devoid of a workpiece of the resonator is contacted to the top face of the mounting table, the mounting table makes a follow-up movement in a suitable direction with respect to the base by the bearing consisting of the spherical projection portion and the spherical depression portion so that the top face devoid of a workpiece becomes parallel to the bonding work face, the mechanical lock clamps the spherical projection portion to the spherical depression portion in this state, and the position of the mounting table can be maintained while the top face and the bonding work face are parallel to each other. When the fixing means comprises an air operation unit for enabling the mechanical lock to carry out clamping and unclamping operations with air, the structure of the fixing means can be made simpler than when the mechanical lock carries out clamping and unclamping operations with mechanical elements. When the fixing means comprises a spring for enabling the mechanical lock to carry out clamping operation, if air for enabling the mechanical lock to carry out clamping and unclamping operations is cut off, the spring can ensure the clamping operation of the mechanical lock.